Switching power supply

ABSTRACT

Methods and systems for enhancing system efficiency in a power amplification, modulation, and transmission system are provided. Embodiments include determining output power characteristics of a selected modulation scheme to be employed in data transmission, determining a most probable output power point of operation for the selected modulation scheme based on the output power characteristics, and controlling the output stage power supply of the system to operate at substantially optimal efficiency at the most probable output power point of operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.11/979,852, filed Nov. 8, 2007 , now allowed, which claims the benefitof U.S. Provisional Patent Application No. 60/857,777, filed Nov. 9,2006 . Each of the foregoing applications is incorporated herein byreference in its entirety.

The present application is related to U.S. patent application Ser. No.11/256,172, filed Oct. 24, 2005, now U.S. Pat. No. 7,184,723 and U.S.patent application Ser. No. 11/508,989, filed Aug. 24, 2006 , both ofwhich are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to modulation and poweramplification and related network and system control functions. Moreparticularly, the invention relates to methods and systems for enhancingsystem parameters including efficiency in power amplification systems.

2. Background Art

The efficiency of a power supply directly affects the efficiency of thepower amplification system using the power supply. Further, in the caseof mobile or portable battery powered wireless devices, the voltage andcurrent requirements of the radio frequency (RF) transmitter used in thedevices are largely determined by the power amplifier technology andsystem requirements.

As such, the power supply efficiency not only affects the efficiency ofthe power modulation and amplification system but also the efficiency ofthe mobile device using the power amplification system.

There is a need therefore for power supply architectures, designtechniques, and operation modes that affect and/or optimize the overallsystem efficiency of the modulation and power amplification system.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to systems and methods of RF powertransmission, modulation, and amplification. Systems and methods of RFpower transmission, modulation, and amplification also referred toherein as Vector Power Amplification (VPA) are described in related U.S.patent application Ser. No. 11/256,172, filed Oct. 24, 2005, now U.S.Pat. No. 7,184,723 and U.S. patent application Ser. No. 11/508,989,filed Aug. 24, 2006, both of which are incorporated herein by referencein their entireties. It is noted that the invention is not limited tothese VPA examples but can be applied to other transmitter functions andcircuitry such as modulators, amplifiers, filters, and controlcircuitry.

The present invention provides methods and systems for enhancing systemefficiency in a power amplification, modulation, and transmissionsystem.

According to embodiments of the present invention, the overall systemefficiency can be affected and/or optimized according to, but notlimited to, the average or most probable output power levels, maximumpower output level, battery voltage and/or changes in battery voltage,amplifier and/or modulator voltage and current requirements, powercontrol requirements, adjacent channel power requirements (ACPR),adjacent channel leakage requirements (ACLR), standing wave ratio (SWR)requirements, in-band noise performance requirements, and out-of-Landnoise performance requirements such as is required by GSM and otherstandards based cell phone signals. In mobile or portable batterypowered devices, this results in extended battery life, smaller batterysize, and increased and/or optimized output power for various poweroutput levels, connectivity range, number of network nodes, andreliability and longevity.

Methods according to embodiments of the present invention includedetermining output power characteristics of a selected modulation schemeto be employed in data transmission, determining a probable (in certainembodiments, a most probable) output power point of operation for theselected modulation scheme based on the output power characteristics,and controlling the output stage power supply of the system to operateat substantially optimal efficiency at the most probable output powerpoint of operation. In an embodiment, the output power characteristicsinclude the probability distribution function of output power using theselected modulation scheme. In another embodiment, the output powercharacteristics are determined according to network statistics.

Provided methods for enhancing system efficiency can be used withtraditional power amplifiers, vector power amplifiers, andmultiple-input-single-output (MISO) power amplifiers (such as, but notlimited to, the VPA examples described in the patent and patentapplication cited above). Further, the methods can be applied withvarious modulation schemes including, but not limited to, GSM, W-CDMA,CDMA 2000, EvDO, EDGE, HSUPA, and OFDM.

Systems implementing the above described methods include a mechanism tobypass the power supply circuitry at a pre-determined threshold, furtherincreasing the system efficiency. In an implementation, a bypass switchcontrol circuitry is used together with the power supply circuitry, tocause the bypass of the power supply circuitry using a bypass switchwhen the pre-determined threshold is exceeded. In an embodiment, thethreshold is defined in terms of output power, and the bypass switch isengaged or disengaged when the output power exceeds or falls below thethreshold. In another embodiment, the power supply is bypassed when thenoise power on or near the output frequency (frequency of the outputsignal) exceeds a threshold.

In an embodiment, the bypass switch threshold can be changed in realtime by wirelessly downloading information to the system. This wirelessinformation can be sent from a wireless network or from another device.In an embodiment, the bypass switch threshold is modified based onbattery voltage. In another embodiment, the bypass switch threshold ismodified based on battery life requirements. In a further embodiment,the bypass switch threshold is modified based on output powerrequirements and/or on power supply current output requirements.

Additional features and advantages of the invention will be set forth inthe description that follows. Yet further features and advantages willbe apparent to a person skilled in the art based on the description setforth herein or may be learned by practice of the invention. Theadvantages of the invention will be realized and attained by thestructure and methods particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described with reference tothe accompanying drawings, wherein generally like reference numbersindicate identical or functionally similar elements. Also, generally,the leftmost digit(s) of the reference numbers identify the drawings inwhich the associated elements are first introduced.

FIG. 1 illustrates exemplary plots of efficiency versus output currentof a typical switching power supply for two exemplary values of outputpower.

FIG. 2 illustrates an example probability density function (PDF) of ahandset output power.

FIG. 3 illustrates exemplary plots of power supply output voltage andpower supply output current versus output power of an examplemultiple-input-single-output (MISO) amplifier.

FIG. 4 illustrates an example step down switching power supply having abypass switch architecture.

FIG. 5 illustrates another example step down switching power supplyhaving a bypass switch architecture.

FIG. 6 illustrates example efficiency enhancement due to the use of abypass switch architecture in a switching power supply.

FIG. 7 illustrates examples of coupling a switching power supply totraditional amplifier designs.

FIG. 8 illustrates examples of coupling a switching power supply tomultiple-input-single-output (MISO) amplifier designs.

FIGS. 9A-9E illustrate the integration of a switching power supply in aD2P vector power amplification system according to an embodiment of theinvention.

FIGS. 10A-10E illustrate the integration of a switching power supply inanother D2P vector power amplification system according to an embodimentof the invention.

FIG. 11 is a process flowchart of a method for enhancing systemefficiency in a power amplification system according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Overview

Methods and systems for enhancing system efficiency in a poweramplification, modulation, and transmission system are provided herein.

According to embodiments of the present invention, the overall systemefficiency can be affected and/or optimized according to, but notlimited to, the average or most probable output power levels, maximumpower output level, battery voltage and/or changes in battery voltage,amplifier and/or modulator voltage and current requirements, powercontrol requirements, adjacent channel power requirements (ACPR),adjacent channel leakage requirements (ACLR), standing wave ratio (SWR)requirements, in-band noise performance requirements, and out-of-bandnoise performance requirements such as is required by GSM and otherstandards based cell phone signals. In mobile or portable batterypowered devices, this results in extended battery life, smaller batterysize, and increased and/or optimized output power for various poweroutput levels, connectivity range, number of network nodes, andreliability and longevity.

According to embodiments of the present invention, the efficiency of alltypes of amplifiers, including, but not limited to, MISO amplifiers canbe improved over various output power levels by designing a variablevoltage switching power supply based on system criteria, such as, butnot limited to, network statistics and/or typical operating conditions.

According to further embodiments, an optional bypass switch architecturecan be used as part of the power supply design to further enhance thesystem efficiency, reduce the system noise floor, and increase theavailable output current of the power supply. These advantages reducethe amount of circuitry required to support multiple modulation methodsand output powers.

Embodiments for enhancing system efficiency can be used with traditionalpower amplifiers, vector power amplifiers, andmultiple-input-single-output (MISO) power amplifiers. Further,embodiments can be applied with various modulation schemes including,but not limited to, GSM, W-CDMA, CDMA 2000, EvDO, EDGE, HSUPA, and OFDM.

Systems implementing some of the above described embodiments include amechanism to bypass the power supply circuitry at a pre-determinedthreshold, further increasing the system efficiency. In animplementation, a bypass switch control circuitry is used together withthe power supply circuitry, to cause the bypass of the power supplycircuitry when the pre-determined threshold is exceeded. In anembodiment, the threshold is defined in terms of output power, and thebypass switch is engaged or disengaged when the output power exceeds orfalls below the threshold. In another embodiment, the power supply isbypassed when the noise power on or near the output frequency (frequencyof the output signal) exceeds a threshold.

Effect of Power Supply Efficiency on System Efficiency

FIG. 1 illustrates exemplary plots 102 and 104 of efficiency versusoutput current of a typical switching power supply for two exemplaryvalues of output power.

As illustrated in plots 102 and 104, the power supply is most efficientwhen the output current is between 100 and 200 milliamps (rna) dependingon the input and output voltages. Also, when plots 102 and 104 areextended beyond 650 rnA for the output current, the power supplyefficiency would continue to decrease as the output current increases.

The power supply efficiency directly affects the efficiency of theentire power amplification system using the power supply. Further, inthe case of mobile or portable battery powered wireless devicesincluding, but not limited to, cellular phones, wireless LAN devices,and WiMax devices and systems, voltage and current requirements of theradio frequency (RF) transmitter are largely determined by the poweramplifier technology and system requirements. As such, the efficiency ofthe power supply of a power amplification system significantly affectsthe efficiency of the mobile device using said power amplificationsystem.

To highlight this problem, consider, for example, a scenario where thebattery voltage (power supply input voltage, VIN) is 3.6 V and theoutput voltage (power supply output voltage, V_(OUT)) is 3.16 V, andwhere the power supply drives a power amplifier that is 50% efficientgenerating a +30 dBm output power. Accordingly, the power supply currentwill be approximately 633 rnA. From plot 102 of FIG. 1, this results ina power supply efficiency of approximately 94%, which is 4% less thanthe optimum 98% achievable with a power supply current of approximately190 rnA.

At lower output voltages (V_(OUT)), as illustrated in plot 104 forexample, the problem becomes more pronounced, and the power supplyefficiency approaches approximately 80% at 633 rnA, which is 18% lessefficient than when the power supply is operating in its optimum voltageand current range.

The effect on system efficiency is significant. For example, when thepower amplifier is operating at 50% efficiency and the power supply isoperating at 94% efficiency, the system efficiency is 0.5×0.94=0.47 or47%. Similarly, when the power amplifier is operating at 50% efficiencyand the power supply is operating at 80% efficiency, the systemefficiency is 0.5×0.8=0.4 or 40%.

Power Supply Design Optimization for Enhanced System Efficiency

In this section, power supply design embodiments to enhance systemefficiency. are provided. For example, switching power supplies can bedesigned to operate in pre-determined output voltage and current rangesthat result in increased efficiency of the power supply and consequentlyin increased system efficiency. These embodiments can be used to controlboth the efficiency and the output power level of traditional poweramplifiers (PAs) and/or multiple-input-single-output (MISO) amplifiers.

One set of criteria that can be used to design both the power supply andthe power amplifier for maximized system efficiency include the networkcharacteristics and/or statistics. An exemplary network characteristicof a code division multiple access (CDMA) network is shown in FIG. 2,which illustrates a probability density function (PDF) 200 of a handsetoutput power used on a reverse link (handset to base station) andmeasured at the power amplifier output of the handset.

PDF 200 is shown according to a log normal scale in FIG. 2 and providesthe time probability that the handset spends transmitting using a givenoutput power level, according to the transmitted CDMA waveform.

Based on PDF 200, it would be sufficient to increase system efficiencyto design a power supply and/or amplifier system that maintains orincreases the system efficiency at power levels below +30 dBm. Indeed,mathematical analysis shows that the mean or expected value of PDF 200is approximately +17 dBm or 50 milliWatts (mW). Further, since theprobability of transmission at +17 dBm is higher than the probability oftransmission at +30 dBm, system efficiency increases at +17 dBm willhave a greater overall effect on extended battery life and/or batterysize than system efficiency increases at +30 dBm.

The above described CDMA design criteria can be applied in the case of amultiple-input-single-output (MISO) amplifier, examples of which aredescribed in the patent and patent application cited above. FIG. 3illustrates exemplary plots 302 and 304 of power supply output voltageand power supply output current, respectively, versus output power of anexample MISO amplifier.

Plots 302 and 304 illustrate the power supply output voltage and outputcurrent that are required by an example MISO amplifier to achieve a CDMApower control range. For ease of illustration, the output power range inplots 302 and 304 is limited to 0 dBm to +30 dBm instead of −40 dBm to+30 dBm, since the most probable output power occurs at +17 dBm.

In an example MISO amplifier, the power supply output voltage is appliedat the collector/drain of the MISO amplifier depending on the MISOamplifier configuration used. As illustrated in exemplary plot 302, thecollector/drain voltage range of the MISO amplifier is +1.39V to +3.6V.Also, for an output power of +17 dBm, the collector/drain voltage of theMISO amplifier is approximately +1.39V.

Accordingly, to achieve the highest system efficiency possible usingexample CDMA PDF 200, the switching power supply should be designed tooperate at its highest efficiency when its output voltage isapproximately +1.39V and, correspondingly from exemplary plot 304, whenits output current is approximately 100 rnA.

Note that the switching power supply may be designed to vary its highestefficiency point of operation according to the selected data modulationand transmission scheme. As would be understood by a person skilled inthe art, the output power characteristics of transmission schemes (e.g.,CDMA, CDMA2000, GSM, etc.) differ from one scheme to another.Accordingly, the most probable output power point of operation alsovaries from one transmission scheme to another, and, consequently, sodoes the highest efficiency point of operation of the power supply.

Based on the above, a method for enhancing system efficiency in a poweramplification system is provided and is illustrated in process flowchart1100 of FIG. 11. The power amplification system can be a traditionalpower amplifier, a vector power amplifier, or amultiple-input-single-output (MISO) amplifier. Process 1100 includessteps 1102, 1104, and 1106.

Process 1100 begins in step 1102, which includes determining outputpower characteristics of a selected modulation scheme to be employed indata transmission. In an embodiment, the output power characteristicsinclude a probability distribution function of output power using theselected modulation scheme. In another embodiment, the output powercharacteristics are determined according to network statistics. Theselected modulation scheme can be any one of GSM, W-CDMA, CDMA 2000,EvDO, EDGE, HSUPA, and OFDM.

Step 1104 includes determining a probable (in certain embodiments, amost probable) output power point of operation for the selectedmodulation scheme based on the determined, output power characteristics.

Step 1106 includes controlling an output stage power supply within thepower amplification system to operate at substantially optimalefficiency at the probable output power point of operation.

Power Supply Efficiency Optimization

In addition to designing/controlling the power supply to operateoptimally in terms of efficiency at the most probable output power, theoverall power supply efficiency can be improved to increase systemefficiency. As will be described in the exemplary embodiments below, thesystem efficiency can be further increased by bypassing the power supplywhen the required output voltage (or the output power) exceeds apre-determined threshold. For example, referring to exemplary plot 302,an optional power supply bypass switch can be used to bypass the powersupply when the power supply output voltage required by the MISOamplifier reaches 3.6V, which corresponds to an output power of +26 dBmor 400 mW. By bypassing the power supply, any loss in system efficiencydue to the power supply efficiency can be eliminated.

FIG. 4 illustrates an example step down (buck) switching power supply400 having a bypass switch architecture.

Power supply 400 receives an input voltage signal V_(IN) 418, an OutputStage Voltage Control signal 416, and a Threshold Voltage signal 414.

Input voltage signal V_(IN) 418 is typically received from a battery andis set according to, among other requirements, the device using thepower amplifier. In exemplary plots 102 and 104, for example, V_(IN) 418takes values of 2.7V, 3.6V, 4.2V, and 5.5V.

Output Stage Voltage Control signal 416 is received from a controlmodule configured to control the power supply voltage provided to theoutput stage of the power amplifier. In example 400, Output StageVoltage Control signal 416 controls an Aperture Generator and Controlmodule 404 of power supply 400.

Threshold Voltage 414 may also be received from the same control ofmodule as Output Stage Voltage Control signal 416. The function ofThreshold Voltage 414 is to control a Bypass Switch Control module 402of power supply 400.

Threshold Voltage 414 may be fixed or programmable. Threshold Voltage414 may vary depending on network statistics and/or network waveformsincluding, but not limited to, GSM, W-CDMA, CDMA2000, EvDO, EDGE, HSUPA,OFDM, or others. In an embodiment, Threshold Voltage 414 can be changedin real time by wirelessly downloading information to the system. Forexample, Threshold Voltage 414 can be downloaded to the mobile device orportable unit using power supply 400 from a network provider. In anotherembodiment, Threshold Voltage 414 can be pre-programmed based onwaveform efficiency requirements and/or modified or adjusted based onbattery life requirements. In a further embodiment, Threshold Voltage414 is modified based on output power requirements and/or on powersupply current output requirements.

Referring back to FIG. 4, in addition to modules 402 and 404, powersupply 400 includes a Bypass Switch 406, an input switch 420, aswitching transistor 408, and an output LC circuit comprised of aninductor L_(OUT) 410 and a capacitor C_(OUT) 412.

Power supply 400 operates in two modes: normal mode and bypass mode.

In normal mode, input voltage signal V_(IN) 418 is received at inputswitch 420, which is controlled by Aperture Generator and Control module404.

Aperture Generator and Control module 404 is configured to control inputswitch 420 to couple input voltage signal V_(IN) 418 to thecollector/drain of switching transistor 408. As such, V_(IN) 418provides a bias voltage for the collector/drain of switching transistor408.

Aperture Generator and Control module 404 is also configured to controlthe base/gate voltage of switching transistor 408, effectivelycontrolling the point of operation and subsequently the gain ofswitching transistor 408. In an embodiment, Aperture Generator andControl module 404 uses Output Stage Voltage Control signal 416 todetermine the required power supply output voltage and, accordingly,controls the base/gate voltage of switching transistor 408. In anotherembodiment, Aperture Generator and Control module 404 receives afeedback signal of the power supply output voltage V_(OUT) 422. ApertureGenerator and Control module 404 may then adjust its control ofswitching transistor 408, if necessary.

In example power supply 400, switching transistor 408 is illustrated asa single NMOS transistor. As would be understood by a person skilled inthe art, embodiments according to the present invention are not limitedby this configuration and may include, among other configurations, oneor more NMOS, PMOS, NPN, and PNP transistors.

At the output (collector/drain node) of switching transistor 408,inductor L_(OUT) 410 is an exemplary output reactance that meets thevoltage and current output requirements of the supply. The reactance canbe inductive or capacitive. C_(OUT) 412 acts to filter the AC componentsof the output of switching transistor 408. As such power supply outputvoltage V_(OUT) 422 is substantially a DC voltage.

In Bypass mode, V_(OUT) 418 is directly coupled to the power supplyoutput node, which provides power supply output voltage V_(OUT) 422.Bypass mode operation is described below.

Bypass Switch Control module 402 receives Threshold Voltage signal 414and Output Stage Voltage Control signal 416. Threshold Voltage signal414 determines at which value of the power supply output voltage powersupply 400 switches to bypass mode. Output Stage Voltage Control signal416 includes information about the target power supply output voltageand thus allows Bypass Switch Control module 402 to determine the valueof the power supply output voltage.

Bypass Switch Control module 402 compares Threshold Voltage 414 and thevalue of the power supply output voltage to determine whether powersupply 400 should switch to bypass mode. When the power supply outputvoltage exceeds Threshold Voltage 414, Bypass Switch Control module 402controls Bypass Switch 406 to couple input voltage signal V_(IN) 418 tothe power supply output node. At the same time, Bypass Switch Controlmodule 402 controls Aperture Generator and Control module 404 to causeit to de-couple input voltage signal V_(IN) 418 from the collector/drainnode of switching transistor 408 and to shut off switching transistor408.

Accordingly, Bypass Switch Control module 402 bypasses the power supplywhen the output power exceeds a determined threshold, thereby increasingthe efficiency of the power supply for output powers exceeding thedetermined threshold. In another embodiment, Bypass Switch Controlmodule 402 bypasses the power supply when the noise power on or near theoutput frequency exceeds a threshold.

As would be understood by a person skilled in the art based on theteachings herein, several parameters can be affected and/or optimizedusing the power supply design of FIG. 4. For example, the operationdynamic range of the power supply is reduced through the bypass option,which increases the efficiency over the smaller power supply controlrange. Also, since the switching portion of the supply does not have tocarry the maximum voltage and current required, the size and value ofthe switch (including the switching inductor or capacitor) can bereduced. Additionally, in-band and out-of-band noise can be reduced asswitching components typically cause noise. This is especially importantat higher power output levels because all cellular phone standards havea maximum “close in” (20 MHz offset) receive band noise floorrequirement. Further, as the battery voltage changes during operation,the higher output power levels can be maintained and controlled over awider battery voltage range.

FIG. 5 illustrates another example step down switching power supply 500having a bypass switch architecture.

Switching power supply 500 is similar in several respects to examplepower supply 400 of FIG. 4. Additionally, switching power supply 500includes an Optional Hysteresis Control signal 502, which is received byBypass Switch Control module 402, and an Optional Load Current SensingCircuit 504.

Operation of Bypass Switch Control module 402 is as follows in exampleswitching power supply 500. Bypass Switch Control module 402 receivesThreshold Voltage signal 414, Output Stage Voltage Control signal 416,and Optional Hysteresis Control signal 502.

Bypass Switch Control module 402 compares the value of Output StageVoltage Control signal 416 to the sum of Threshold Voltage signal 414and Optional Hysteresis Control signal 502.

When Output Stage Voltage Control signal 416 exceeds the sum ofThreshold Voltage signal 414 and Optional Hysteresis Control signal 502,Bypass Switch Control module 402 controls Aperture Generator and Controlmodule to cause it to de-couple input voltage signal V_(IN) 418 from thecollector/drain node of switching transistor 408 and to shut offswitching transistor 408. At the same time, Bypass Switch Control module406 controls Bypass Switch 406 to couple input voltage signal V_(IN) 418to the power supply output node 506.

On the other hand, when Output Stage Voltage Control signal 416 fallsbelow the sum of Threshold Voltage signal 414 and Optional HysteresisControl signal 502, Bypass Switch Control module 402 controls BypassSwitch 406 to de-couple input voltage signal V_(IN) 418 from the powersupply output node 506 and re-activates transistor 408 by coupling inputvoltage signal V_(IN) 418 thereto through input switch 420.

Optional Hysteresis Control signal 502 can be downloaded or otherwiseprovided to the mobile device or portable unit using power supply 500from a network provider. In another embodiment, Optional HysteresisControl signal 502 can be pre-programmed based on waveform efficiencyrequirements and/or modified or adjusted based on changes in batteryvoltage and/or required output power.

Optional Load Current Sensing Circuit 504 is coupled at output node 422of power supply 500. In an embodiment, Load Current Sensing Circuit 504senses load current to determine any variations that may affect powersupply output voltage V_(OUT) 506. Further, Optional Load CurrentSensing Circuit 504 provides a feedback signal to Bypass Switch Controlmodule 402. In an embodiment, the feedback signal includes informationabout sensed load current, which can be used by Bypass Switch Controlmodule 402 to control the operation mode of switching power supply 500.

The power supply design techniques discussed above have been describedwith respect to step down switching power supplies. Embodiments of thepresent invention are not limited to these embodiments. As would beunderstood by a person skilled in the art based on the teachings herein,the power supply design techniques described herein can be applied tostep down switching power supplies (buck), step up switching powersupplies (boost), and step down and step up (buck-boost) power supplies.

FIG. 6 is an example graph 600 that illustrates efficiency enhancementdue to the use of a bypass switch architecture in a switching powersupply. In example 600, the switching power supply is optimized for a+17 dBm output (1.39V output voltage and 100 rnA output current).

Efficiency curve 602 represents the efficiency versus the output currentof the switching power supply without a bypass switch. Efficiency curve604 represents the efficiency versus the output current of the switchingpower supply with a bypass switch. Note that the two efficiency curves602 and 604 overlap with each other over the output current range from 0to approximately 0.4 A.

Without a bypass switch, as illustrated by efficiency curve 602, theswitching power supply has its highest efficiency between 70 and 100 rnAof output current, which renders the highest system efficiency of theexemplary MISO amplifier in the example network statistics.

On the other hand, with a bypass switch architecture, as illustrated byefficiency curve 604, the power supply efficiency can be furtherincreased when the output current exceeds 400 rnA. This in turnincreases the network system efficiency when the required output poweris equal to or greater than 400 mW (+26 dBm).

The optional bypass switch architecture can also be used to increase themaximum current range of the power supply design. For example, if theswitching power supply circuitry (without the bypass switch) can supplya maximum of 650 rnA but the bypass switch is designed to support up to1500 rnA, the power supply can as a result supply up to 1500 rnA. Thebypass switch has yet another advantage, which includes the suppressionof switching noise or ripple presented to the amplifier when the bypassswitch is engaged and the switching power supply is turned off. Thisresults in a reduced system noise floor when the bypass switch isengaged.

In what follows, the positioning/integration of the switching powersupply within a power amplifier design or a system using the poweramplifier design is described.

FIG. 7 illustrates examples 702 and 704 of coupling a switching powersupply to traditional amplifier designs. In example 702, the switchingpower supply, represented by voltage signal V_(OUT), is coupled(optionally through a pull-up resistance) to the collector/emitter nodeof an NPN/PNP-based amplifier. Similarly, in example 702, the switchingpower supply, represented by voltage signal V_(OUT), is coupled(optionally through a pullup resistance) to the drain/source node of anNMOS/PMOS-based amplifier.

FIG. 8 illustrates similar examples 802 and 804 of coupling a switchingpower supply to multiple-input-single-output (MISO) amplifier designs.Example 802 illustrates the coupling of the switching power supply,represented by voltage signal V_(OUT), to an exemplary two-input singleoutput BJT-based (NPN/PNP/Hybrid) MISO amplifier. The switching powersupply can be coupled (optionally through a pull-up resistance) to thecommon collector/emitter node of the MISO transistors. Similarly,example 804 illustrates the coupling of the switching power supply,represented by voltage signal V_(OUT), to an exemplary two-input singleoutput FET-based (NMOS/PMOS/Hybrid) MISO amplifier. The switching powersupply can be coupled (optionally through a pull-up resistance) to thecommon drain/source node of the MISO transistors.

The switching power supply (with optional bypass switch architecture)can be used to increase the system efficiency of the exemplarytraditional and MISO amplifier designs described above. Further, theswitching power supply (with optional bypass switch architecture) can bedesigned to operate with and optimize the system efficiency of any ofthe MISO amplifier architectures and schematics shown in related U.S.patent application Ser. Nos. 11/256,172 and 11/508,989.

FIGS. 9A-9E illustrate an example D2P Vector Power Amplification system5900, which uses an embodiment of the switching power supply describedherein to power its output stage. The output stage of system 5900includes two MISO amplifiers MA1 5930 and MA2 5932. The switching powersupply is integrated in system 5900 as Output Stage Power Supply module5906, shown in FIG. 9B. The switching power supply receives an OutputStage Voltage Control signal 5765 and outputs two output stage supplyvoltage signals MA1 Output Stage VSupply 5911 and MA2 Output StageVSupply 5913, which power MA1 5930 and MA2 5932, respectively. Furtherdescription of system 5900 can be found in related U.S. patentapplication Ser. No. 11/508,989, incorporated herein by reference in itsentirety.

FIGS. 10A-10E illustrate another example D2P Vector Power Amplificationsystem 6100, which uses an embodiment of the switching power supplydescribed herein to power its output stage. The output stage of system6100 includes five MISO amplifiers GMA2 6126, MA3 6128, MA4 6130, GMAO6132, and MA1 6134. The switching power supply is integrated in system6100 as Output Stage Power Supply module 5906, shown in FIG. 10B. Theswitching power supply receives an Output Stage Voltage Control signal5765 and outputs five output stage supply voltage signals GMAO OutputStage VSupply 6113, MA1 Output Stage VSupply 6114, GMA2 Output StageVSupply 6115, MA3 Output Stage VSupply 6116, and MA4 Output StageVSupply 6117, which power MISO amplifiers GMAO 6132, MA1 6134, GMA26126, MA3 6128, and MA4 6130, respectively. Further description ofsystem 5900 can be found in related U.S. patent application Ser. No.11/508,989, incorporated herein by reference in its entirety.

Embodiments of the switching power supply and bypass switch designtechniques described herein can be applied to any modulation and/oramplification circuitry or stage within a multi-stage amplificationsystem, to enhance the system efficiency. For example, in addition tobeing applied to the output stage of MISO amplifiers MA1 5930 and MA25932, embodiments described herein can be applied to a Driver Stageand/or a Pre-Driver Stage within each of MISO amplifiers MA1 5930 andMA2 5932. As such, power supplies designed to power up theseamplification stages (e.g., Driver Stage Power Supply 5904 in FIGS. 9Band 10B) can be configured to operate in optimum voltage and currentranges to provide increased system efficiency.

In other embodiments, the Driver Stage Power Supply and the Output StagePower Supply can be combined into a single switching power supplydesign. The combined switching power supply may or may not employ abypass switch architecture depending on the system design requirements.

Conclusion

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments, but should be defined only in accordance with thefollowing claims and their equivalents.

1. A method comprising: determining power efficiency characteristics ofan amplifier for a selected modulation scheme to be employed in datatransmission; controlling an output stage power supply of the amplifierto operate at a first voltage, wherein the amplifier provides a firstoutput current with a first power efficiency higher than a predeterminedvalue at the first voltage; and adjusting the output stage power supplyof the amplifier to operate at a second voltage when the first powerefficiency falls below the predetermined value, wherein the amplifierprovides a second output current with a second power efficiency higherthan the predetermined value at the second voltage.
 2. The method ofclaim 1, the wherein determining comprises determining a probabilitydistribution function of the power efficiency characteristics for theselected modulation scheme.
 3. The method of claim 1, wherein thecontrolling comprises determining a probable output power point ofoperation for the selected modulation scheme based on the powerefficiency characteristics.
 4. The method of claim 1, wherein thecontrolling comprises operating the amplifier with an output currentthat provides a maximum power efficiency at the first voltage value. 5.The method of claim 1, wherein the controlling comprises down-convertingan input voltage to the first voltage, wherein the input voltage has avoltage value substantially equal to the second voltage.
 6. The methodof claim 1, wherein the adjusting comprises adjusting the output stagepower supply of the amplifier to operate at the second voltage based ona comparison of a threshold voltage to the first voltage.
 7. The methodof claim 1, wherein the adjusting comprises detecting a load current atan output stage of the amplifier.
 8. An apparatus comprising: an inputvoltage; an output voltage node; an aperture generator and controlmodule configured to control a switching transistor to output adown-converted voltage based on the input voltage, wherein a firstoutput current with a first power efficiency higher than a predeterminedvalue is provided to the output voltage node; and a bypass switchcontrol module configured to: control the aperture generator and controlmodule to deactivate the switching transistor; and provide the inputvoltage to the output voltage node when the first power efficiency fallsbelow the predetermined value, wherein a second output current with asecond power efficiency higher than the predetermined value is providedto the output voltage node.
 9. The apparatus of claim 8, furthercomprising: a load current sensing circuit configured to detect a loadcurrent at the output voltage node.
 10. The apparatus of claim 8,wherein the aperture generator and control module is configured tocontrol the switching transistor based on a probable output power pointof operation for a selected modulation scheme based on power efficiencycharacteristics of an amplifier.
 11. The apparatus of claim 8, whereinthe aperture generator and control module is configured to provide thefirst output current at a maximum power efficiency associated with thedown-converted voltage.
 12. The apparatus of claim 8, wherein the bypassswitch control module is configured to provide the input voltage to theoutput voltage node based on a comparison of a threshold voltage to thedown-converted voltage.
 13. A system comprising: an amplifier; and aswitching power supply coupled to the amplifier, wherein the switchingpower supply comprises: an input voltage; an output voltage node; anaperture generator and control module configured to control a switchingtransistor to output a down-converted voltage based on the inputvoltage, wherein a first output current with a first power efficiencyhigher than a predetermined value is provided to the output voltagenode; and a bypass switch control module configured to: control theaperture generator and control module to deactivate the switchingtransistor; and provide the input voltage to the output voltage nodewhen the first power efficiency falls below the predetermined value,wherein a second output current with a second power efficiency higherthan the predetermined value is provided to the output voltage node. 14.The system of claim 13, wherein the amplifier comprises amultiple-input-single-output (MISO) amplifier.
 15. The system of claim13, wherein the switching power supply is coupled to a collector or anemitter terminal of a BJT-based amplifier.
 16. The system of claim 13,wherein the switching power supply is coupled to a drain or a sourceterminal of a MOS-based amplifier.
 17. The system of claim 13, whereinthe switching power supply comprises a load current sensing circuitconfigured to detect a load current at the output voltage node.
 18. Thesystem of claim 13, wherein the aperture generator and control module isconfigured to control the switching transistor based on a probableoutput power point of operation for a selected modulation scheme basedon power efficiency characteristics of the amplifier.
 19. The system ofclaim 13, wherein the aperture generator and control module isconfigured to provide the first output current at a maximum powerefficiency associated with the down-converted voltage.
 20. The system ofclaim 13, wherein the bypass switch control module is configured toprovide the input voltage to the output voltage node based on acomparison of a threshold voltage to the down-converted voltage.